The goal of our studies is to understand the structure and function of several genetic regulatory signals in the E. coli chromosome. These signals are nucleotide sequences associated with operons which, when recognized by one or more specific proteins, determine whether or not the operons are expressed. Once having determined the basic sequence structure of a given set of signals, we hope to learn what the functional significance of various parts of the sequence are. We specifically plan to: (1) determine the sequence changes involved with all known lac operon promoter mutations, (2) determine the step at which each lac promoter mutation alters the RNA polymerase-lac promoter interaction, (3) sequence the threonine operon promoter and determine its relationship to the structural genes, and (4) determine a transcription map of the tet and kan transposition elements and localize their promoters. BIBLIOGRAPHIC REFERENCES: Mitchell, D., Reznikoff, W., and Beckwith, J. (1976). Genetic fusions that help define a transcription region in E. coli. J. Mol. Biol., 104, 441. Reznikoff, W.S. (1976). Formation of the RNA polymerase-lac promoter open complex. RNA Polymerase. Cold Spring Harbor Laboratory, in press.